This invention relates to a battery handle which may be connected interchangeably to a variety of electrically dependent instruments. More specifically, this invention deals with such a handle which may accept either two non-rechargeable batteries, or a single rechargeable battery having different lengths. When using a rechargeable battery, the unit may be recharged either by directly plugging the handle unit into a U.S. standard electrical outlet or by use of a suitable transformer as an intermediate.
Health professionals use a variety of small hand-held diagnostic instruments such as otoscopes, ophthalmoscopes and retinoscopes in order to perform a variety of functions. Optimal flexibility and portability is achieved by using battery operated versions of such instruments. The use of non-rechargeable batteries, however, is expensive, requires storage and frequent changes of batteries, and is environmentally unsound.
On the other hand, the use of rechargeable batteries that are recharged in separate rechargers is cumbersome and requires a fair amount of attention. Thus, having the ability to recharge a battery while it remains in the device is desirable, and has been incorporated into a number of devices, such as flashlights (U.S. Pat. Nos. 3,281,637 and 3,096,941).
However, such rechargeable units present a different problem in that prolonged use of the device drains the battery, which then takes a substantial amount of time to recharge. During the recharge period, which exceeds the time period of usability, the handle, and thus the instrument, is unusable. U.S. Pat. No. 4,147,163, assigned to present assignee, and U.S. Pat. No. 4,382,219 both address this problem by each providing a handle for a medical instrument that is capable of accepting either a rechargeable or non-rechargeable batteries.
Such dual battery units must overcome a number of potential problems. The first problem is that single or pairs of standard non-rechargeable batteries are not generally interchangeable with a rechargeable battery used in such instruments. A second problem is that an inadvertent attempt to charge a non-rechargeable battery can result in excessive heat, expansion of the battery, and the possible danger of an explosion. A third problem is that an inadvertent inversion of rechargeable batteries may result in a short circuit, destroying the batteries. A fourth problem is that when using a rechargeable battery having a side wall terminal, if this terminal is allowed to contact the handle, the handle will become excessively warm or even dangerously hot. A fifth problem associated with convertible battery handles stems from the fact that a single rechargeable battery and a pair of non-rechargeable batteries are of different lengths. In order to accommodate the different length combinations, the battery handle, typically, is overly long and the instrument attached thereto is unbalanced and difficult to manipulate, particularly by a person having small hands.
While some of these problems are addressed by the prior art, all of these problems are not handled. Also, two additional features are desirable. First it would be preferable for the unit to contain as few mechanically movable parts as possible, for ease and economy of production as well as for durability. Second, since the instruments involved may be used outside of the U.S., it is desirable for the handle to be adaptable to allow the batteries to be charged in other current/voltage combinations than those used within the U.S. by allowing direct linkage with a suitable transformer.